Communication systems currently exist to allow a call to be interconnected between different communication networks. For example, a call can be originated in a cellular network for a destination in a wireline network. These calls can be dialed and interconnected through a gateway telephony device, such as Private Branch Exchange (PBX) server, for example. Typically, such interconnection includes an originating cellular device sending the digits for a destination device telephone number in a Dual-Tone Multi-Frequency (DTMF) format in digitized audio packets to the gateway device. The gateway provides the connection between the wireless and wireline networks, and thereafter allows the originating device and destination device to perform the call negotiation.
A problem arises in non-3 G communication systems in that there is no data connection along with the audio connection. Therefore, the gateway only receives the audio packets, and is unable to separately authenticate the originating device. As a result, an unauthorized device could contact the gateway with dial tones for an unauthorized destination device and obtain service illegitimately.
Another problem arises when DTMF tones are digitized and sent with different codecs. Some of the available lower bandwidth or higher compression codecs could distort the audio tones to such an extent that they may no longer be recognized as DTMF tones. Still another problem occurs when portions of the originating call are dropped. For example, the gateway, may receive a telephone number with missing or incorrect digits. In this case, the gateway may not be able to complete the call, or could even call the wrong telephone number.
Accordingly, there is a need for a technique to lower the probability that an unauthorized or erroneous call can occur between communication networks.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The system and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.